1. a. A spherical object or entity: a steel ball. b. A spherical or almost spherical body: a ball of flame. 2. Sports a. Any of various rounded, movable objects used in various athletic activities and games. b. Such an object moving, thrown, hit, or kicked in a particular manner: a low ball; a fair ball. c. A game, especially baseball or basketball, played with such an object. d. A pitched baseball that does not pass through the strike zone and is not swung at by the batter. 3. a. A solid spherical or pointed projectile, such as one shot from a cannon. b. Projectiles of this kind considered as a group. 4. A rounded part or protuberance, especially of the body: the ball of the foot. 5. balls Vulgar Slang a. The testicles. b. Courage, especially when reckless. c. Great presumptuousness.